1. Field of the Invention
The present invention relates to an endoscope having a hardness adjusting means for adjusting the hardness of a flexible part of an insertion unit thereof.
2. Description of the Related Art
In recent years, endoscopes by which various kinds of therapies and treatments can be conducted have been widely adopted. An elongated insertion unit of such an endoscope is inserted into the body cavity, whereby a region to be tested in the body cavity is observed without an incision. If necessary, a treatment appliance may be passed through a treatment appliance channel in the endoscope.
The insertion unit of the endoscope is flexible so as to be inserted into a bent body cavity. However, since the insertion unit has plasticity, it becomes difficult to reliably convey manipulations, which are performed at the proximal part of the insertion unit, to the distal part thereof. This leads to the deteriorated ability of the distal part of the insertion unit to respond to manipulations performed at the proximal part thereof. Consequently, a problem arises in that since the direction of the distal part is not determined, it becomes hard to insert the insertion unit smoothly into an intended region.
For overcoming the problem, for example, Japanese Unexamined Utility Model Publication No. 3-43802 has disclosed an endoscope having a hardness adjusting means(or a hardness varying means) incorporated therein. The hardness adjusting means is composed of an elongated coil and wire. An operator who conducts an endoscopic examination performs a simple manipulation to adjust the plasticity of the flexible part of the insertion unit. This makes it easy to insert the insertion unit into a bent channel.
The hardness adjusting means has a elongated coil and a wire lying through the elongated coil. Both ends of the coil and wire are firmly fixed by brazing to bases formed at both ends of a flexible tube serving as armor of a plastic tube of an endoscope.
If the hardness adjusting means is used repeatedly, the elongated coil deteriorates. The natural length thereof may be shortened. In this case, if the wire were pulled, the distal end of the flexible tube would be pulled more greatly than it is pulled before the elongated coil deteriorated. An unnecessarily large load may then be imposed on the flexible tube. Consequently, there arises a fear that the flexible tube will be twisted or will deteriorate.
Moreover, when the hardness adjusting means is driven forcefully, the elongated coil may be buckled or the wire may be broken. Otherwise, the coil or wire may deteriorate significantly. In this case, it becomes impossible to replace the coil or wire with a new one.